The present invention relates to a digital-television-broadcast receiving apparatus for receiving digital television broadcasts such as digital satellite broadcasting service.
As a television broadcasting system using a stationary satellite, a digital broadcasting system has been introduced in addition to an analog broadcasting system. The digital broadcasting system is capable of presenting a plurality of signals each representing a television broadcast program, in which a plurality of signals compressed by using typically an MPEG technique, are multiplexed into one carrier.
A digital-television-broadcast receiving apparatus selects a carrier conveying multiplexed television broadcasting programs, which a user desires to watch, in accordance with a command issued by the user. Then, the selected carrier is demodulated to generate a transport stream in which pieces of compressed data of a plurality of television broadcast programs are multiplexed.
Compressed data of a desired television broadcast program is then extracted from the transport stream. Subsequently, the extracted compressed data of the desired television broadcast program is decompressed and, then, an analog output video signal and an analog output audio signal are generated from digital data obtained as a result of the decompression. The analog output video signal and the analog output audio signal are used to reproduce images and sounds of the desired television broadcast program.
By the way, in recent years, the digital television broadcasting system using a stationary satellite also allows various kinds of digital data of the so-called web pages or homepages and the so-called game programs to be broadcasted to the user by inserting them into a broadcast signal. A web page and a game program are described in a special language such as an HTML (Hyper Text Makeup Language) or a language known as the MHEG (Multimedia and Hypermedia Information Coding Experts Group).
However, received digital data of a web page or a game program can not be utilized without further processing the data. In the case of a web page described in a special language such as the HTML, for example, the presented web page is analyzed by using software known as the so-called browser to produce display data for displaying the web page. To put it in detail, a video signal for displaying the web page is generated from the display data before the web page can be displayed.
In order to receive and utilize information such as a web page presented by the digital television broadcasting system by means of a digital-television-broadcast receiving apparatus, it is necessary to provide the digital-television-broadcast receiving apparatus with a graphic processing unit and a buffer memory. The graphic processing unit generates a video signal for displaying a web page from display data produced by the browser. Besides, used in processing to display a web page, the buffer memory has a storage capacity large enough for storing an image of the volume of at least one screen.
As described above, a graphic processing unit and a buffer memory are newly required in order to utilize information such as a web page presented by the digital television broadcasting system. In this case, the digital-television-broadcast receiving apparatus becomes expensive, increasing the magnitude of a load to be borne by the user.
The present invention provides a digital-television-broadcast receiving apparatus capable of implementing a new function of utilizing new information presented by a digital television broadcasting system without increasing the cost of the apparatus.
According to one aspect of the present invention, there is provided a digital-television-broadcast receiving apparatus including a tuner for selecting a carrier-wave component including a signal of a broadcast program selected by a command issued by the user, a front-end unit for demodulating the carrier-wave component selected by the tuner and outputting a transport stream, a selected-program extracting unit for extracting compressed data of the broadcast program selected by the command issued by the user from the transport stream output by the front-end unit, a decompression unit for decompressing the compressed data extracted by the selected-program extracting unit and for outputting a signal for presenting the selected broadcast program, a graphic processing unit for generating a signal for presenting an image based on input data by conversion of the input data into display data such as characters, figures and symbols provided in advance, and a working memory with a storage capacity large enough for storing image data of the volume of at least one screen to be shared by the decompression unit and the graphic processing unit as a storage unit common to the decompression unit and the graphics processing unit. The digital-television-broadcast receiving apparatus, wherein the selected-program extracting unit is capable of extracting presentation information included in the transport stream in accordance with a command issued by the user, a data converting unit receives the presentation information extracted by the selected-program extracting unit, converts the presentation information into input data with a format acceptable to the graphic processing unit and supplies the input data to the graphic processing unit, and the graphic processing unit generates image data for presenting images for the presentation information from the input data converted by the data converting unit by using the working memory as a work area.
In the digital-television-broadcast receiving apparatus provided by the present invention as described above, the selected carrier-wave component (the carrier) of a digital television broadcast conveys multiplexed presentation information such as compressed data of a plurality of broadcast programs, web pages and game programs other than compressed data of a television broadcast program. The carrier of the digital television broadcast is supplied to the front-end unit for demodulating the carrier to produce a transport stream, which is then supplied to the selected-program extracting unit.
The selected-program extracting unit extracts compressed data of a television broadcast program and presentation information other than the television broadcast program from the transport stream in accordance with a command issued by the user. Assume that a user selects a desired television broadcast program. In this case, the selected-program extracting unit extracts compressed data of the selected television broadcast program, supplying the compressed data to the decompression unit. The decompression unit decompresses the compressed data by using the working memory as a work area in order to play back and output the television broadcast program selected by the user.
When the user selects presentation information other than the television broadcast program, on the other hand, the selected-program extracting unit extracts the selected presentation information, supplying the desired presentation information to the data converting unit. The data converting unit converts the presentation information into input data with a format acceptable to the graphic processing unit, supplying the input data to the graphic processing unit.
The graphic processing unit generates a video signal for displaying images for the presentation information from the input data received from the data converting unit by using the working memory as a work area.
It is thus possible to generate a video signal for displaying images for presentation information other than a television broadcasting program by using the working memory used in the decompression processing and to display the images for the presentation information to the user.
In this way, it is possible to display images for presentation information conveyed by a digital television broadcast without the need to newly install a dedicated working memory. Thus, since it is possible to utilize presentation information conveyed by a digital television broadcast without the need to newly install a dedicated working memory, the cost of the apparatus for receiving digital television broadcasts does not rise.
According to another aspect of the present invention, in the digital-television-broadcast receiving apparatus described above, the transport stream includes multiplexed program-table data for displaying a program table showing a plurality of broadcasting programs multiplexed in the transport stream, the selected-program extracting unit extracts the program-table data from the transport stream in accordance with a command issued by the user and supplies the program-table data to the graphic processing unit, and the graphic processing unit converts the program-table data into display data in order to generate image data for displaying the program table.
As described above, in addition to compressed data of a plurality of television broadcasting programs and presentation information which are multiplexed in the carrier of a digital television broadcast, the carrier also conveys typically multiplexed program-table data for displaying a program table showing a plurality of television broadcasting programs.
The selected-program extracting unit is also capable of extracting program-table data selected by a command issued by the user. Program-table data extracted by the selected-program extracting unit is supplied to the graphic processing unit. The graphic processing unit generates a signal for displaying a program table from the program-table data by using the working memory as a work area. As a result, the program table is displayed and presented to the user.
As described above, the graphic processing unit and the working memory are used in processing to display a program table. Thus, the working memory is used not only in decompression processing, but also in processing to display presentation information or a program table. In addition, the graphics processing circuit can also be used in both the processing to display presentation information and a program table.
As a result, it is not necessary to provide separate work areas for the compression processing and processing to display presentation information and a program table. By the same token, it is also not necessary to provide separate graphics processing units for the processing to display presentation information and a program table.
For the above reason, the configuration of the apparatus for receiving digital television broadcasts can be made simple and the cost of the apparatus can be prevented from rising.
According to still another aspect of the present invention, in the digital-television-broadcast receiving apparatus as described, the presentation information is described in a predetermined language, and the data converting unit carries out processing to analyze the presentation information to generate input data with a format acceptable to the graphic processing unit from the presentation information.
An example of the presentation information described in the predetermined language is a web page described in the HTML. Such a web page is conveyed by a digital television broadcast.
Assume that the user issues a command to use, for example, a selected web page, a sort of presentation information which is conveyed by a digital television broadcast to a user. In this case, the selected-program extracting unit extracts web data which forms a web page, supplying the data to the data converting unit. In the data converting unit, the web data is subjected to an HTML analysis, being converted into input data with a format acceptable to the graphic processing unit. The graphic processing unit then generates a signal for displaying the web page from the input data received from the data converting unit.
In this way, images of presentation information described in a predetermined language such as a web page can be reproduced as an output that can be utilized by the user. In this case, since neither dedicated working memory nor dedicated graphic processing unit for displaying the presentation information is needed as described above, the cost of the apparatus for receiving digital television broadcasts can be prevented from rising and the facility for utilizing presentation information can be implemented relatively with ease.
According to a further aspect of the present invention, in the digital-television-broadcast receiving apparatus described above, the presentation information is a program including image information, and the data converting unit executes the program to generate input data with a format acceptable to the graphic processing unit using the image information.
For example, a program including image information such as a game program is conveyed by a digital television broadcast as presentation information.
Assume that the user issues a command to use for example a selected game program, which is a sort of presentation information conveyed by a digital television broadcast. In this case, the selected-program extracting unit extracts the desired game program, supplying the game program to the data converting unit. In the data converting unit, the game program is executed to generate input data with a format acceptable to the graphic processing unit using image information included in the game program. The input data is subsequently supplied to the graphic processing unit which then generates a signal for displaying images for image information included in the game program.
In this way, images used in a game program can be played back and output by execution of the game program. That is to say, by executing a game program, a game presented by a game program can be enjoyed.
In this case, since neither dedicated working memory nor dedicated graphic processing unit for displaying the presentation information is needed as described above, the cost of the apparatus for receiving digital television broadcasts can be prevented from rising and the facility for utilizing presentation information including image information such as a game program can be implemented relatively with ease.
According to a still further aspect of the present invention, the digital-television-broadcast receiving apparatus described above is further provided with a connector for connecting an external memory, and an interface circuit for fetching information from the external memory connected to the connector by way of the connector, wherein the data converting unit executes a program loaded from the external memory connected to the connector for generating input data with a format acceptable to the graphic processing unit from the presentation information extracted by the selected-program extracting unit in order to generate the input data.
As described above, in order to generate input data with a format acceptable to the graphic processing unit from presentation information extracted by the selected-program extracting unit, a program to be executed by the data converting unit is loaded from the external memory connected to the connector by way of the interface circuit.
As a result, even in the case of a digital-television-broadcast receiving apparatus without a program for generating input data with a format acceptable to the graphic processing unit from presentation information, the required function of such a program can be added by using an external memory which stores the program. In this way, a function to utilize presentation information conveyed by a digital television broadcast can be added with ease.